(a) Technical Field
The present invention relates to a dual muffler, and more particularly, to a dual muffler that emits a sporty exhaust sound and minimizes heat transfer of exhaust gas to the surroundings of the dual muffler.
(b) Background Art
In general, a muffler is a device that reduces noise generated from an internal combustion engine, and requires a balanced design to satisfy all noise effects and engine output because resistance against exhaust gas flow increases to reduce the engine output when the noise effect increases.
Meanwhile, in order to implement an exhaust sound that provides a more sporty sound of the dual muffler, it is important to reduce high frequency noise as much as possible and to increase rumble noise in within a low frequency and middle frequency bandwidth properly.
FIG. 1 shows the structure of an existing dual muffler including a plurality of baffles 2 in a housing 1 to partition the internal space of the housing 1 into a plurality of chambers 3a, 3b, 3c, 3d, and 3e. An end of an inlet pipe 4 is located in the fifth chamber 3e while the inlet pipe 4 penetrates the third chamber 3c formed in the center of the housing 1 and the fourth chamber 3d neighboring the third chamber 3c, and ends of an auxiliary pipe 5 penetrating the second chamber 3b are located in the first chamber 3a and the third chamber 3c, respectively. Ends of a first outlet pipe 6a penetrating the first chamber 3a and the second chamber 3b are located on a side of the housing 1 and on the third chamber 3c, and ends of a second outlet pipe 6b penetrating the fourth chamber 3d and the fifth chamber 3e are located on the opposite side of the housing 1 and on the third chamber 3c. 
That is, exhaust gas introduced through the inlet pipe exits the fourth chamber, passes through the third chamber, and then exits into a tail pipe through the first outlet pipe and the second outlet pipe. However, in existing dual muffler rumble noise is not enough to implement a really effective sport like sound because the exhaust noise is dampened and weakened by expansion and interference while the exhaust gas passes through the fourth and third chambers.
Moreover, since the first chamber, the third chamber, and the fourth chamber are regions exposed directly to the exhaust gas, the third and fourth chambers, particularly, are on the path through which the exhaust gas flows and thus heat transferred to components surrounding the housing such as the trunk and a bumper. These components over time could become damaged from the heat.
The above-described background art is intended only for understanding of background of the present invention, but should not be considered as an already known prior art to one of ordinary skill in the art.